The tissue culture Core C will supply all investigators with colorectal carcinomas cells (CRC), fibroblasts, and B-lymphocytes. The core will maintain an available bank of well-characterized cell lines of CRC and will monitor the quality of the cell lines by testing for expression of tumor-associated antigens and mycoplasma infections, and for identity by DNA fingerprinting. New permanent cell lines will be established either directly from patients' lesions or after growth of tumors in SCID mice. These immunodeficient animals will also serve to produce larger quantities of tumor material for biochemical studies. The Core C is staffed by highly experienced personnel, who are intimately familiar with all the necessary techniques and who have demonstrated expertise in the tissue culture field.